What temp??

[armyrat1970]

Thanks for the input guys.
Pretty wide range of temps here. 650-820.
My mold is a LEE double cavity.

Hi Vance. I also use Lee molds. My 357, 45 and 30carbine are double cavity. My 8mms are single cavity. I have found, that contray to popular belief, the Lee aluminum molds take a little while to heat up evenly. And cool rather quickly. I now use a hot plate, at the highest setting, to heat the mold and run my temps between 780 and 800.
I have bad eyes and start to get a little crosseyed after dropping 30 to 50 boolits from my Lee 20 pounder. I then take a break. Throw my sprues back into the pot. Set my mold on the hot plate. Check my boolits and throw the rejects back into the pot. Smoke a cig and drink a beer. Check to make sure my temps are back up to 780 or 800 with my RCBS thermometer. Than start casting again, until I start getting a little crosseyed again. Then I do the process over.
I have tried different alloy temps with the Lee molds and it doesn't seem to keep the mold hot if lower than 780 to 800. At 600 or 650 I can drop 10 or so boolits, with the first ones coming out a little frosted, but after the 10 or so, they start getting wrinkles because the mold is cooling down.
Now with your molds dropping 400gr boolits, you may find the mold may heat up a little quicker. Because there is less meat around the cavity. But they may also cool down quicker. Because there is a little less meat around the cavity to hold the heat.
You may need to run you alloy temps a little higher. 800 to 820. Gives you a reason to use that RCBS thermometer.
I would start with a really hot mold and the alloy temps being around 780. Drop a couple of boolits and check them. Drop 20 more and check the last two. If all is right, roll with it. If you're starting to get some wrinkles, however slight, crank your temps up a little. On your alloy.

[Vance in Ak]

760F is a good place to start if you are using an RCBS ladle and a single DC Al mold.

MJ

Lee production pot

[Changeling]

It's the one and only RCBS 45-270 SAA. Alloys was between 650 and 700 degrees, I was casting fast and cooling mold just a little on a wet sponge after every 3 pours.

Humbo if you don't mind my asking, what alloy were you using, they are some of the best castings I have ever see on this forum.

[HORNET]

Vance, the real starting point is the melting temperature of your alloy. I can cast quite well with 50/50 WW/Lino at a temperature that barely gets pure lead melted (with some molds). Bass Ackwards claimed a couple of years ago that you should start 100 degrees above the melting temp for iron molds and 200 degrees above it for aluminum molds. That seems to work as a good starting point for me but may need modified depending on the amount of fine detail in the cavities, the number of cavities, and several other factors. YMMV

[Humbo]

Thanks for the input on my boolits guys.
@Changeling: Thank you. This thread was initially about ww alloy, the boolits in the picture were cast with an alloy with 2 parts ww and 1 part lino. I added the lino just to bring the hardness up a little, I get similar results with straight ww alloy when I do my part.

I'm pretty anal about my casting, but it pays off. I prep the molds properly, then I bring them up in temperature to the point where I get slightly frosted boolits. Then I figure out how often I have too cool the molds just to avoid any frosting. It's easier to get the mold a little too hot and then bring it down to temperature, than the other way around. It takes me a couple of tries, but after that, I can cast hundreds and even thousands of boolits, with no rejects. The picture is taken of a box with about 20 pounds of boolits in it, and I didn't take out one single reject after I got going. And I cast fast, as fast as I can as long as I keep the cooling consistent. I also keep the sprue puddle as consistent as I possibly can.

For example, with an alloy temperature of 650-700 degrees, casting with the RCBS 45-270SAA I cool the mold about one second on a moist sponge after every 3 pours. It's not always needed, but it keeps the mold temperature consistent. I keep the sprue plate just cool enough that I don't get any tearing in the center of the base where the sprue plate holes are when cutting the sprue. This is pretty far from the point where you start to get smeared bases. Sprues are a bit harder to cut, but bullet weight is very consistent and bases turn out perfect. I cool the top of the mold, when keeping the melt below 700 degrees I hardly ever have to cool the bottom of the mold at all.

I have similar techniques for other molds. The Lee 2-cavity molds are a bit more tricky. Lately I have been casting loads of the .501-440 WFN. This is a big boolit, which means less meat on the mold. Casting with an alloy at the same temp, I have to cool both top and bottom of the mold after every pour, about 2 seconds on the top and about half that time on the bottom. Still keeping the sprue puddle consistent, about the size of an US quarter. Frosting usually starts to occur at the center of the base. Try to keep this area as small as possible, and don't let it reach the circumference of the boolit. Casting like this, I get less than 2 grains of variation on a boolit that drops at 450 grains. And this is from a 20 dollar mold.

This was a couple of examples on how I do my casting with a couple of my molds. Lyman and LBT molds require slightly different casting teqniques and cooling frequencies, SAECO's are pretty similar to the RCBS. It pretty much depends on the size of the boolit, as long as the melt temperature and casting pace is the same.

Good casting!